Gene Mapping: Why It Matters How Many Times Ancient Man Mated With Denisovans

A new study published in Cell revealed that ancient man mated with Denisovans and Neanderthals. About 1 to 6 percent of Denisovan genes are present in modern man, but information on this ancient population is limited.

Sharon Brown of the University of Washington looked for evidence of the persistence of Denisovan DNA in the human gene pool, and findings suggest ancient man mated with this little-known hominin population at least twice.

Researchers compared genomes of people from China and Japan to the pinky found from a Denisovan woman in Siberia’s Altai region. Two waves of Denisovan DNA suggest that modern man’s ancestor mated with the ancient hominin at least twice in the Late Pleistocene.

East Asians, Tibetans, and people from Oceania and Papua New Guinea carry fragments of DNA from Denisovans. Denisovan DNA in modern man’s genome might explain unique gene variants and conditions that once puzzled scientists.

Explanation For Autoimmune Diseases

Mating is a full-proof method for passing on genes. In 2011, a Stanford University study looked into the genome of Denisovans and Neanderthals in search for immunity markers. The research focused on the genes that identify and destroy pathogens that could pose a danger to the body — the HLA class I genes.

As reported by The Guardian, breeding with Denisovans is most likely to blame for passing on HLA-B*73 gene which is common in West Asia where the mating is believed to have happened. Since Denisovans existed before modern man, their genes have adapted to the environment. Passing on these genes boosted the immunity of the new generation, but not without a “downside.”

Genetic variations brought about by genes passed on by ancient ancestors could explain why some people are susceptible to autoimmune diseases and why some don’t have high immunity. In fact, the study revealed that most of the autoimmune diseases could be traced back to Denisovans’ alleles. Since modern man can’t handle the passed-on genetic traits, they result to the immune system attacking the body like other pathogens and viruses, leading to what is known today as an autoimmune disease. Traits which would have benefited hominins in ancient times could be maladaptive given the current lifestyle of the modern man.

Unique Adaptation Traits

According to Discover Magazine, there’s one beneficial gene modern man inherited from Denisovans. Rasmus Nielsen of the University of California Berkeley reported that modern Tibetans could live in an altitude of 4,000 meters because of their EPA1 gene. This gene prevents blood thickening and helps them live in extraordinary conditions.

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The said gene regulates hemoglobin in the blood making it possible to live in oxygen-thin environments up to 13,000 feet. The unique DNA sequence is different from other genes in human groups and more identical to Denisovan DNA.

Another beneficial trait passed on by Denisovans found in people from Greenland comes in the form of a gene that alters body fat distribution, allowing people to survive cold climates.

Based on these findings, Denisovans mating with ancient man’s ancestors might have been crucial for the development of survival traits, allowing the species to evolve and survive extreme conditions in ancient times.